Newly added functions of portable devices require the corresponding enhancement of efficiency and battery life. Therefore, the design of the portable devices faces the problems of how to reduce the power consumption for extending battery life and standby time. On the other hand, the development of the smart phone market leads the continuous growth of memory shipments. In the future, larger memory capacity is required for portable devices. Therefore, the issue of how to reduce the power consumption of memory is being emphasized.
For the power consumption of memory in portable devices, it is necessary to develop technologies for effectively reducing the power consumption of memory by the partial array self refresh (PASR) function.